In general, a fuel cell system mounted in a fuel cell vehicle performs a pressurization operation to control an operative pressure of each fluid to improve an output of a fuel cell.
Typically, the fuel cell stack may be in a form in which a plurality of fuel cells is stacked and sealing of each cell is maintained by using several hundreds of gaskets.
When a difference in pressure of each fluid supplied to the cell is equal to or greater than a predetermined level in the fuel cell stack, a sealing may easily deteriorate due to a structure of the fuel cell stack and system operation safety and performance may deteriorate when leakage occurs.
Particularly, in the related art, when a temperature of a cooling system of the fuel cell increases rapidly, pressure at an entrance of the stack may be elevated to an upper limit value by volume expansion of a coolant, such that an output of a fuel cell vehicle may be frequently limited, and further, when pressure of a channel of a coolant is rapidly elevated due to a boundary of a separation plate inside the stack, leakage inside the stack may frequently occur.
Accordingly, the fuel cell system in the related art has been developed to avoid over pressure of a coolant by compulsorily decreasing an operation speed of a pump which circulates the coolant to a fuel cell stack. However, the related art may have disadvantages. For example, the operation speed of the pump may decrease although cooling of the stack is necessary.
Meanwhile, a coolant operative pressure in the fuel cell system in the related art may be determined according to a specification of a pressurizing cap mounted at an upper side of a radiator for radiating heat of the coolant discharged from the stack.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.